PIEZOELECTRIC MICROMECHANICAL ENERGY HARVESTERS

• US 20120206016A1
• Filed: 02/13/2012
• Published: 08/16/2012
• Est. Priority Date: 02/11/2011
• Status: Active Grant

• Current Assignee: Georgia Tech Research Corporation (University System of Georgia)
• Original Assignee: Georgia Tech Research Corporation (University System of Georgia)
• Inventors: Ayazi, Farrokh, Sorenson, Logan, Fu, Jenna
• Granted Patent: US 8,680,752 B2
• Time in Patent Office: Days
• US Class Current: 310/339
• CPC Class Codes: F03G 7/08 recovering energy derived from swinging, rolling, pitching or like movements, e.g. from the vibrations of a machine
• CPC Class Codes: H02N 2/188 adapted for resonant operation

Abstract

The present invention comprises systems, apparatuses, and methods for harvesting ambient mechanical energy at a lower frequency and transforming the harvested energy into electrical energy at a higher frequency. Transforming the energy from relatively lower input frequency energy to relatively higher output frequency energy can help realize greater efficiencies found at higher frequencies. Because the input plane of the ambient mechanical energy is not always predictable, some embodiments of the present invention comprise both in-plane and out-of-plane energy harvesters that produce an electrical output in multiple planes.

Claims

1. A micromechanical device, comprising:

an energy harvester comprising;

a proof mass that receives ambient mechanical energy at a first frequency in a first plane;

a transducer comprising piezoelectric material; and

a transfer mechanism that transfers the received ambient mechanical energy to the transducer, causing the transducer to vibrate at its resonance frequency to create an electrical output energy at the resonance frequency to upconvert the frequency of the ambient mechanical energy to harvest energy.

2. The micromechanical device of claim 1, wherein proof mass, transducer and transfer mechanism are monolithically integrated on a single substrate.

3. The micromechanical device of claim 2, wherein the transducer and proof mass are in a common plane with the single substrate.

4. The micromechanical device of claim 1, wherein the transfer mechanism comprises only mechanical components.

5. The micromechanical device of claim 1, wherein the transfer mechanism is a nonlinear mechanical effect.

6. The micromechanical device of claim 1, wherein the received ambient mechanical energy or transfer mechanism is a collision or impact.

7. The micromechanical device of claim 1 further comprising a sensor component.

8. The micromechanical device of claim 7, wherein the sensor component, proof mass, transducer, and transfer mechanism are monolithically integrated on a single substrate.

9. The micromechanical device of claim 7, wherein the sensor component is in electrical communication with the energy harvester.

10. The micromechanical device of claim 7, wherein the sensor component is integrated with the energy harvester.

11. The micromechanical device of claim 7, wherein the sensor component is selected from the group comprising a gravimetric sensor and the transducer.

12. The micromechanical device of claim 7, wherein the sensor component is an accelerometer.

13. The micromechanical device of claim 12, wherein the output of the sensor component is proportional to the applied external acceleration.

14. The micromechanical device of claim 7, wherein the sensor component is covered by a functional layer.

15. The micromechanical device of claim 14, wherein a sensor component resonance frequency depends on a quantity of a substance attached or adsorbed to/on the functional layer.

16. The micromechanical device of claim 7, wherein the sensor component comprises the proof mass and a support spring system.

17. The micromechanical device of claim 1, wherein the proof mass comprises a beam having a first mass at a first end of the beam and a second mass at a second, opposite end of the beam, wherein the first mass is greater than the second mass.

18. The micromechanical device of claim 17, wherein the transfer mechanism is a side wall of the mechanical energy harvester that receives an impact from the first mass when the first mass is accelerated towards the side wall due to the received ambient mechanical energy.

19. The micromechanical device of claim 18, wherein the transfer mechanism further comprises a deformation of the beam caused by the striking of the first mass against the side wall, wherein the deformation causes the second end of the proof mass to vibrate at the resonance frequency.

20. The micromechanical device of claim 19, wherein the transfer mechanism further comprises a first spring that connects the proof mass to the transducer, wherein the spring compresses and relaxes due to the vibration of the second end of the proof mass.

21. The micromechanical device of claim 20, wherein the transfer mechanism further comprises a plurality of second springs attached to the proof mass.

22. The micromechanical device of claim 20, wherein the first spring is a spiral pivot spring design.

23. The micromechanical device of claim 1, wherein the proof mass is a seismic mass that vibrates within the first plane upon receiving the ambient mechanical energy.

24. The micromechanical device of claim 23 further comprising:

a proof mass micro-pick attached to the proof mass;

a transducer micro-pick attached to the transducer; and

wherein proof mass micro-pick causes the transducer to vibrate at the resonance frequency by striking the transducer micro-pick when the received ambient mechanical energy is of a predetermined value.

25. The micromechanical device of claim 24, wherein the transducer is a first spring transducer.

26. The micromechanical device of claim 25 further comprising:

one or more second transducers that vibrate at a second resonance frequency;

a plurality of second proof mass micro-picks attached to the proof mass;

a plurality of second transducer micro-picks attached to the one or more second transducers; and

wherein the plurality of second proof mass micro-picks load the plurality of second transducer micro-picks upon vibration of the proof mass, causing the one or more second transducers to vibrate at the second resonance frequency.

27. The micromechanical device of claim 23, further comprising a second seismic mass that vibrates within a second plane upon receiving the ambient mechanical energy in a second plane.

28. The micromechanical device of claim 1, wherein the transducer and transfer mechanism comprise a plurality of beam transducers attached to the proof mass, wherein the proof mass vibrates at the first frequency and one or more of the beam transducers vibrate at the resonance frequency.

29. The micromechanical device of claim 1, wherein the piezoelectric material is selected from the group comprising lead zirconate titanate, aluminum nitride, zinc oxide, lead magnesium niobate-lead titanate, gallium phosphate, quartz, tourmaline, and polyvinylidene fluoride and its copolymers.

30. An electrical energy generation device, comprising:

a mechanical energy harvester; and

an electrical system connected to the mechanical energy harvester to receive electrical energy from the mechanical energy harvester, wherein the mechanical energy harvester comprises;

a proof mass that receives ambient mechanical energy at a first frequency in a first plane;

a transducer comprising piezoelectric material; and

a transfer mechanism that transfers the received ambient mechanical energy to the transducer, causing the transducer to vibrate at its resonance frequency to create an output voltage at the resonance frequency to upconvert the ambient mechanical energy.

31. The electrical energy generation device of claim 30, wherein the proof mass comprises a beam having a first mass at a first end of the beam and a second mass at a second, opposite end of the beam, wherein the first mass is greater than the second mass.

32. The electrical energy generation device of claim 31, wherein the transfer mechanism is a side wall of the mechanical energy harvester that receives an impact from the first mass when the first mass is accelerated towards the side wall due to the received ambient mechanical energy.

33. The electrical energy generation device of claim 32, wherein the transfer mechanism further comprises a deformation of the beam caused by the striking of the first mass against the side wall, wherein the deformation causes the second end of the proof mass to vibrate at the resonance frequency.

34. The electrical energy generation device of claim 33, wherein the transfer mechanism further comprises a first spring that connects the proof mass to the transducer, wherein the spring compresses and relaxes due to the vibration of the second end of the proof mass.

35. The electrical energy generation device of claim 34, wherein the transfer mechanism further comprises a plurality of second springs attached to the proof mass.

36. The electrical energy generation device of claim 34, wherein the first spring is a spiral pivot spring design.

37. The electrical energy generation device of claim 30, wherein the proof mass is a seismic mass that vibrates within the first plane upon receiving the ambient mechanical energy.

38. The electrical energy generation device of claim 37 further comprising:

a proof mass micro-pick attached to the proof mass;

a transducer micro-pick attached to the transducer; and

wherein proof mass micro-pick causes the transducer to vibrate at the resonance frequency by striking the transducer micro-pick when the received ambient mechanical energy is of a predetermined value.

39. The electrical energy generation device of claim 30, wherein the transducer and transfer mechanism comprise a plurality of beam transducers attached to the proof mass, wherein the proof mass vibrates at the first frequency and one or more of the beam transducers vibrate at the resonance frequency.

40. The electrical energy generation device of claim 30, wherein the piezoelectric material is selected from the group comprising lead zirconate titanate;

aluminum nitride;

zinc oxide;

lead magnesium niobate-lead titanate, gallium phosphate, quartz, tourmaline, and polyvinylidene fluoride and its copolymers.

41. A method for harvesting ambient mechanical energy, the method comprising:

vibrating a proof mass at a first frequency in a first plane upon receipt of the ambient mechanical energy at the proof mass;

providing a transducer comprising piezoelectric material; and

transferring the received ambient mechanical energy to the transducer, causing the transducer to vibrate at its resonance frequency to create an electrical output energy at the resonance frequency.

42. A method of manufacturing a micromechanical energy harvester, comprising:

providing substrate with a deposition layer on the topside of the substrate comprising aluminum nitride between a bottom molybdenum layer and a top molybdenum layer;

etching a first portion of a harvester pattern into the top molybdenum layer;

depositing silicon dioxide on the backside of the substrate;

etching a second portion of the harvester portion into the silicon dioxide deposited on the backside of the substrate;

reducing silicon dioxide deposited on the backside of the substrate;

exposing a bottom electrode on the topside of the substrate;

etching trenches into the topside of the substrate to define a plurality of features of the harvester; and

etching the backside of the substrate to release a proof mass from the substrate.

43. The method of claim 42 further comprising etching the topside of the wafer to form shock stops on the energy harvester.

44. The method of claim 42, wherein the substrate is a silicon-on-insulator wafer.

45. The method of claim 42, wherein the proof mass and a transducer comprising the harvester are in a common plane.

46. The method of claim 42, wherein the micromechanical energy harvester is monolithically constructed from the same substrate.